The military has fielded armored vehicles that have incorporated multiple grenade launching systems to protect the personnel inside from enemy threats. The problem with these vehicles has been the inability of the crew to easily and quickly check the operability of the grenade launching system. There has never been a grenade simulator available that exactly duplicates the physical and electrical characteristics of the actual grenade used.
In the past a grenade was fired by the launcher by applying a sufficient voltage to the grenades terminals to produce approximately one ampere of current. This current flows through an internal electrical match to electrical ground. The match then ignites, which in turn ignites the charge in the grenade. Once this match has ignited, the electrical connection to ground is broken.
The characteristics of an actual grenade are that it shows between 1 and 11/2 ohms of resistance to ground across its terminals before firing and an open circuit to ground after firing. This action takes place in approximately 3 milliseconds.
The prior art test unit was nothing more than an empty grenade case with an indicator lamp which lighted during grenade launcher tests, and two jacks for checking circuit continuity connected in parallel across the lamp.
This test set was unsatisfactory for testing the grenade launching system because it required two people to operate the system and it did not present the required 1 to 11/2 ohms to ground as the actual electrical match required. In addition, the prior art test equipment did not open the circuit to ground once it was used.
Other test simulators tried substituting a 1 ampere fuse across the test electrical terminals. This was not suitable because the 1 ampere would not blow due to the characteristics of the firing circuit, necessitating the use of a 1/4 ampere fuse. This was not satisfactory because the 1/4 ampere fuse shows 2.3 ohms to ground instead of the required 1 ohm. In addition, it is difficult to detect whether the fuze was good to start with and hard to detect when it was blown. A further detriment to the use of a fuze was that an ohm meter was required to check continuity because of the visual problem. Another problem with the 1/4 ampere fuze was that it could only be used once and that gave the wrong current draw to the system and did not represent the current draw of an actual electric match. Since the system would not work if a fuze was not available, large supply of fuses must be maintained on hand.
The attempt to use a circuit breaker in place of a fuze was not feasible because a circuit breaker in this current range requires too long a pulse to operate and would be of the wrong resistance reading.
Other prior art test simulators utilizing an indicator meter were unsatisfactory because they did not meet the 1 to 11/2 ohm resistance requirement prior to testing, failed to open the circuit to electrical ground, required two people to operate and made it extremely difficult to monitor more than one launch tube at a time since the meter must be continually watched to observe its movement indicating a fire pulse has been present.